The Institute of Medicine identified sufficient sleep as one of the leading health behavior objectives for Healthy People 2020. Older (high-school-aged) adolescents are especially vulnerable to insufficient sleep as pubertal changes to sleep regulation (sleep homeostasis and circadian timing) increasingly favor alertness later into the evening and night, making an early sleep onset difficult, and these biological changes coincide with early high school start times. Thus, many high schoolers (aged 14-17 years) are faced with a conflicting biological drive to fall asleep late and a social drive to wake early for school. Approximately 80 to 90% of older adolescents in the U.S. report an average of 1 to 2 h less sleep than recommended on school nights. Sleep restriction is associated with many negative outcomes, including an increased risk for depressed mood and suicidal ideation, poor decision making, poor academic grades, and obesity. The broad objective of this project is to develop an effective, yet feasible intervention to extend school-night sleep duration of older adolescents. This application is in response to PA-11-063, which calls for ...developing and refining novel health-related behavioral interventions specifically targeting adoption or maintenance of health behavior. We propose to develop and test a feasible behavioral intervention to increase school-night sleep duration by advancing the circadian system and providing a time management plan for after-school activities in youngsters most at risk for insufficient school-night sleep - high school students who experience difficulties falling asleep at a desired early time on school nights. Study 1 (intervention development) will examine effectiveness and acceptability of two different durations (30 mins & 90 mins) of morning advancing bright light compared to room light (tested in the lab on one weekend). We will time the bright light based on new data from adolescents collected in our lab. We will use the results of Study 1 in Study 2 (proof of intervention concept), which utilizes morning bright light on one weekend spent in the lab. Weekend wake time - and the start of bright light - and bedtime will shift earlier to advance the circadian system to facilitate earlier sleep onset during the subsequent school week. A school-night time management plan will also be implemented to facilitate these earlier bedtimes. Circadian phase, sleep, neurobehavioral functioning and mood will be measured before and immediately after the intervention and compared to a control group who keeps their usual sleep schedules at home, does not come to the lab for weekend bright light treatment, and is not given any after-school time-management instruction. Long-term effectiveness will be examined after a 3-week maintenance period, during which adolescent will be instructed to follow their earlier and longer sleep schedule and use occasional bright light on weekend mornings at home. Adherence and acceptability of the intervention will be assessed. These data will provide evidence-based treatment strategies for delayed and sleep-restricted adolescents, and acceptability of and adherence to the treatment in this age group.